When it comes to electrical systems on trucks and trailers, it’s all about the wiring. Vehicle safety depends on it—and those connections rely on good maintenance. Truck-Lite has put together an excellent list of guidelines for proper maintenance as follows:

1. Never use a test probe to pierce wire insulation when troubleshooting lighting complaints. Wicking action takes place through any exposed copper stranded wire, which causes moisture to travel along the strands and corrode
critical connections.

2. Understanding the supply voltage is critical to having a safe lighting system. To correct voltage problems, discover the real cause. Under-voltage often is caused by poor electrical connections. To correct under-voltage, don’t just turn up the voltage—find the caused of the under-voltage problem.

3. Many discarded lamps are still in good condition. Play detective when solving lamp problems. First, test with a meter, power supply, or battery. Truck-Lite’s 97100 tester is an excellent tool for this, then if you desire, open the lens on a discarded lamp and examine the bulb. It will tell you why it failed. For example:

•A bulb with stretched or broken filaments was subjected to vibration.
•A yellowish, whitish or bluish glaze on the bulb indicates a rupture in the bulb glass envelope.
• A dark metallic finish indicates old age.
• A black, sooty bulb indicates a poor seal in the bulb.

4. Test all lamps one more time before discarding them. Truck-Lite said its warranty department reports that up to 20% of all lamps sent back are still in good operating condition. The ones that aren’t working can be turned over to your lamp supplier.

5. All lamps will live longer if they run cool. Dirt on the lens increases the heat; so keep them as clean as possible, being careful to use the proper cleaning agents that do not attack the plastic lens materials.

6. Treat the electrical system as you would the chassis. Lubricate certain sockets, pigtails, battery terminals and connections with NYK 77 “non-conductive” anti-corrosion compound. The purpose of the sealant is to totally encapsulate and protect against corrosion and water. Some sealed connectors may not reconnect properly if too much dielectric grease is used. Make sure secondary locks will snap into place when reinstalling connectors. Always follow the manufacturers guidelines for applying dielectric grease.

7. Inspect for improper ground connections. This is a major cause of lamps not working, especially when the chassis is used for a ground. When lamps are grounded through the lamp housing or terminal, make sure there is a clean connection (i.e., metal-to-metal). Also, a fifth wheel ground strap may be used for added ground potential on the chassis ground system.

8. Look for loose, bare or unsupported wire and fixtures. Harnesses and wiring should be on the underside of top frame members rather than on the bottom, where dirt and road splash collect.

9. Always replace wiring, trailer light cables and harnesses with an equal or heavier gauge of wire than was used in the original specifications. If you don’t, it may cause voltage supply problems.

10. On older trucks, avoid cranking the truck when lights or accessories are on, as this can cause premature filament failure. Never leave markers and hazard lights on when parked against a dock. Melted lenses are a sign the vehicle has been parked against a dock while the lights were on.

11. Inspect the grommets that house the lamps. As they age, they eventually will deteriorate from sunlight, ozone and harmful chemicals. New grommets restore shock protection, add security and improve appearance.

12. The use of solvents that are not compatible with polycarbonate or acrylic will result in the softening, crazing and/or cracking of the plastic part.

Questions as to compatibility of other specific materials should be directed to the manufacturer and/or your lighting supplier.